Rushing to the pharmacy two blocks from his home, 32-year-old David Chen in Shanghai found Ban Lan Gen (isatis root 板蓝根) capsules were sold out again. He rushed to three more pharmacies last weekend and again was disappointed since the traditional Chinese medicine has been in great demand.

There was a run on pharmacies selling the patent medicine in the SARS outbreak in 2003, the H1N1 bird flu in 2009 and now with H7N9 bird flu, since many people believe it can prevent these infections.

Ban Lan Gen has been used widely since ancient times as an antibiotic, antiviral and antiseptic in TCM.

But TCM doctors say it's too soon to say whether this patent medicine is effective with this virus and urge people not to take medicine blindly. They urge people to boost the immune system naturally at this time, with garlic, ginger, astragalus (huang qi ??ü?) and other herbs and foods.

Lu Yingdi, a 53-year-old housewife, has stopped buying poultry and pork and goes directly to the seafood and aquatic food sections of markets. Many families do the same and the cost of vegetables, seafood and freshwater foods is increasingly expensive.

Jess Jiang, who has a six-month-old baby, was at a loss when she heard that the H7N9 bird flu virus was detected in pigeons. Pigeon egg yolk has been important in the baby's diet since she started supplementary solid food. She chose pigeon eggs over chicken eggs for general safety reasons.

"Yolk is crucially important for the baby's brain growth," says Jiang. "I can easily remove chicken or pork, but I don't know how to replace yolk."

Jiang says that a friend has thrown out all the eggs in her refrigerator, but she cannot decide what to do.

H7N9 bird flu, which has claimed seven lives in China, has created anxiety since the first case was reported in February. By yesterday, 24 H7N9 cases had been confirmed in China - 11 in Shanghai (including five deaths), eight in Jiangsu Province, three in Zhejiang Province (including two deaths), and two in Anhui Province.

Experts say it does not appear to spread from person to person. It is spread by poultry, but birds show no symptoms. One man who died had butchered pork, but a link between poultry, pork and humans is not clear.

Public speculation

Health officials say there is no apparent connection between the flu and the thousands of dead pigs, many infected with a porcine-only virus. The drinking water has been declared safe.

But with the outbreak of the latest strain of bird flu, people are worried and taking their own precautions.

Though airborne transmission is not suspected, many people are buying face masks. Many are buying disinfectant. Ban Lan Gen sales are rocketing.

Avoiding all poultry and pork is the conventional wisdom. Eggs and freshwater fish have been recently added. In the popular imagination, dead pigs in the rivers must make the fish unsafe to eat; experts rule this out.

Despite widespread public speculation about the dead pigs and new bird flu, there is no solid evidence of a connection so far, according to Dr Tang Jie, director of respiratory medicine at Yueyang Hospital attached to the Shanghai University of TCM.

No H7N9 infections have been reported in Jiaxing, Zhejiang Province, the source of most dead pigs, and no bird flu virus has been found in the dead pigs. All this suggests that avoiding pork, a staple in the Chinese diet, is unnecessary to prevent H7N9 so far.

As for poultry, as long as they are well-cooked, they are safe to eat, says Dr Tang. "The virus is vulnerable to high heat. It can be killed easily in two minutes at 100 degrees Centigrade, and in 30 minutes at 65 degrees."

However, it is relatively resistant to low temperatures and can survive in an environment below 4 degrees Centigrade for a month. Refrigerated and frozen poultry should always be well cooked.

The Chinese patent drug Ban Lan Gen has proved helpful in preventing H1N1 flu and ordinary flu like H3N2, but it is too soon to say whether it is effective in preventing infection by the H7N9 virus, according to Zhong Nanshan, a renowned respiratory disease expert and an academician of Chinese Academy of Engineering. He told reporters last Friday that medicine should not be taken blindly, especially not by healthy people.

The newly emerged H7N9 virus is a mutated avian flu virus that has a relatively high death rate in humans.

"The virus infects the lungs quickly when entering the body; that's why most patients are already in serious condition when they go to the hospital," says Dr Tang. He strongly suggests people go to the hospital immediately if they have flu symptoms.

The H7N9 patients shared some symptoms with ordinary flu patients such as high fever, as well as muscle aches and headache.

A new type of injected flu drug, Peramivir, was approved in China on Sunday as a potential treatment. TCM doctors are working on prescriptions to relieve the symptoms.

Since there is no evidence the virus is transmitted between people, individual prevention is easier.

Basic advice

Avoid direct contact with birds.

Don't eat uncooked or half-cooked foods.

Process and store cooked and uncooked meat separately.

Wear gloves when handling uncooked meat, if hands are cut.

Wash hands frequently.

Airing rooms is helpful in preventing any infectious disease.

Wear gauze masks when flu symptoms occur.

According to TCM, as long as healthy qi (energy flow) circulates fluently, "pathogenic" energies cannot invade. Therefore, improving healthy qi boosts immunity and can help prevent bird flu, according to TCM.

Getting enough sleep and rest is important for the immune system, as is eating a balanced, healthy diet with plenty of fruits and vegetables. TCM herbs that treat the common cold can also help boost immunity. They include detoxifying, "pathogenic-heat" expelling herbs such as honey suckle, wild chrysanthemum, and lian qiao (fructus forsythia á??ì), as well as yang-activating herbs like green onion and ginger. Astragalus or huang qi is famous for improving immunity.

TCM precautions

In response to public inquiries, provinces around China are releasing advice on flu prevention. In addition to the basics - avoiding poultry, cooking food thoroughly and washing hands frequently - they suggest various TCM herbs to boost immunity.